Display screen or portion thereof with a transitional graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with a transitional graphical user interface showing a first image in a sequence of a first embodiment of a new design;

FIG. 2 is a second image thereof;

FIG. 3 is a third image thereof;

FIG. 4 is a fourth image thereof; and

FIG. 5 is a fifth image thereof;

FIG. 6 is a front view of a display screen or portion thereof with a transitional graphical user interface showing a first image in a sequence of a second embodiment of the new design;

FIG. 7 is a second image thereof;

FIG. 8 is a third image thereof;

FIG. 9 is a fourth image thereof; and,

FIG. 10 is a fifth image thereof.

The appearance of the transitional images sequentially transitions between the images shown in FIGS. 1-5 in the first embodiment and between the images shown in FIGS. 6-10 in the second embodiment. The process or period in which one image transitions to another image forms no part of the claimed design.

The outermost broken line rectangle illustrates a display screen or portion thereof. The remaining broken lines illustrate portions of a graphical user interface. The broken lines form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with a transitional graphical user interface, as shown and described. 